The present invention relates to optical crossconnect switches and, more particularly, to an Nxc3x97N crossconnect switch implemented using wavelength routers combined with space switches.
In high capacity optical networks, an essential device is the Nxc3x97N crossconnect switch. The function of this device is to provide, at each node, full connectivity among several incoming fibers, each carrying several wavelength channels. The switch must be nonblocking, and it must be fast and efficient. If N is not too large, these properties can be realized by using a single Nxc3x97N wavelength router combined with tunable transmitters capable of producing N wavelengths. However, this technique is only feasible if the size N of the router is not too large. This is because as N increased, the Nxc3x97N router was difficult to realize in integrated form with satisfactory performance of low loss and low crosstalk, and each transmitter had to provide N wavelengths.
With the ever-increasing capacity of optical networks there is continuing need for even larger Nxc3x97N crossconnect switches.
In accordance with the apparatus of the present invention, the problem of implementing a Nxc3x97N crossconnect switch, for large N, is solved by using an arrangement of smaller wavelength routers combined with space switches. In the prior art, a large Nxc3x97N switch implemented using a router was difficult to realize in integrated form, with satisfactory performance of low loss and low crosstalk, and each transmitter had to provide N wavelengths. According to the present invention, the number of router wavelengths is reduced by a factor m and the Nxc3x97N crossconnect switch is constructed in three stages using space switches and smaller routers. The input and output space switches can be implemented using crossbar or Clos type construction. In the crossbar construction, the input and output switches are 1xc3x972 and 2xc3x971 switches respectively. In the Clos construction, the input stage uses mxc3x97(2mxe2x88x921) space switches and the output stage uses (2mxe2x88x921)xc3x97m space switches. In both the crossbar or Clos type construction, the reduced size of the center stage, using (N/m)xc3x97(N/m) wavelength routers, allows efficient realization in integrated form. Using input space switches with tunable transmitters, each with N/m wavelengths, provides full non-blocking connectivity of the Nxc3x97N crossconnect switch. In one arrangement, the input and output space switches are implemented using 2xc3x972, 1xc3x972, and 2xc3x971 switch elements. In one input space switch embodiment, a data modulator is combined with the 2xc3x972 switch elements and integrated on a single wafer. Each input and output space switch can be realized with negligible crosstalk by using a dilated arrangement.
More particularly, my invention is directed to an Nxc3x97N nonblocking optical switch for providing a connection between any of N inlets and any of N outlets, the Nxc3x97N switch comprising
an input stage including a plurality of input space switches, each input of each of the input space switches connects to a different one of the N inlets;
an output stage including a plurality of output space switches, each output of each of the output space switches connects to a different one of the N outlets; and
a center stage connected between the input stage and the output stage, the center stage including a plurality of N/mxc3x97N/m wavelength routers, wherein a connecting link is provided between each N/mxc3x97N/m wavelength router and each input or output switch, so that each N/mxc3x97N/m wavelength router connects to each input space switch and each output switch.